chp 16 Flashcards
16.1A Explain the basic function of the autonomic nervous system (ANS):
The ANS regulates involuntary physiological functions, including heart rate, blood pressure, digestion, respiratory rate, and glandular activity. It maintains homeostasis by controlling smooth muscle, cardiac muscle, and glands without conscious control.
List the divisions of the autonomic nervous system and describe the conditions under which each is more influential:
Sympathetic Division – Dominant during stressful or emergency situations (“fight or flight”); increases heart rate, dilates pupils, inhibits digestion.
Parasympathetic Division – Dominant during rest (“rest and digest”); slows heart rate, promotes digestion and energy conservation.
Enteric Nervous System (ENS) – Manages the digestive tract independently but can be influenced by sympathetic and parasympathetic divisions.
Dominant during stressful or emergency situations (“fight or flight”); increases heart rate, dilates pupils, inhibits digestion.
sympathetic division
Dominant during rest (“rest and digest”); slows heart rate, promotes digestion and energy conservation.
Parasympathetic division
Manages the digestive tract independently but can be influenced by sympathetic and parasympathetic divisions.
Enteric Nervous System (ENS)
Describe the structural and functional differences between the somatic nervous system and the ANS:
Somatic Nervous System (SNS): Voluntary control of skeletal muscles, involves a single motor neuron from CNS to effector.
ANS: Involuntary control of smooth and cardiac muscle and glands, involves two neurons (preganglionic and postganglionic) in series from CNS to effector
Describe the relationship between preganglionic and postganglionic neurons:
Preganglionic neurons originate in the CNS and synapse with postganglionic neurons in autonomic ganglia. The postganglionic neurons extend from the ganglia to target effectors.
Contrast somatic and autonomic motor neurons with sensory neurons:
Motor Neurons: Carry commands from the CNS to muscles and glands.
Somatic: One neuron, voluntary.
Autonomic: Two neurons, involuntary.
Sensory Neurons: Transmit sensory input from the body to the CNS.
Motor Neurons
Carry commands from the CNS to muscles and glands.
sensory neurons
Transmit sensory input from the body to the CNS.
somatic neurons vs autonomic neurons
Somatic: One neuron, voluntary.
Autonomic: Two neurons, involuntary.
list the divisions of the ANS
Sympathetic Division
Parasympathetic Division
Enteric Nervous System (ENS)
Describe the arrangement of sympathetic neurons and ganglia:
Sympathetic preganglionic neurons originate in the thoracolumbar region of the spinal cord and synapse in sympathetic chain ganglia or collateral ganglia near the spinal cord. Postganglionic neurons extend to target organs.
Describe the arrangement of parasympathetic neurons and ganglia
Parasympathetic preganglionic neurons originate in the brainstem or sacral spinal cord and synapse in terminal ganglia located near or within the target organs. Postganglionic neurons are short.
Explain what an autonomic nerve plexus is and list the major autonomic nerve plexuses in the body:
An autonomic nerve plexus is a network of sympathetic and parasympathetic axons. Major plexuses include:
Cardiac plexus
Pulmonary plexus
Celiac (solar) plexus
Superior mesenteric plexus
Inferior mesenteric plexus
Hypogastric plexus
Discuss the organization of the ENS:
The ENS consists of two major plexuses in the gastrointestinal tract:
Myenteric plexus: Controls gastrointestinal motility
Submucosal plexus: Regulates enzyme secretion, blood flow, and absorption
It can operate independently of the CNS.
Explain dual innervation of the ANS:
Most organs receive input from both sympathetic and parasympathetic divisions, often with opposing effects (e.g., sympathetic increases heart rate, parasympathetic decreases it).
Describe the role of the sympathetic division during activity or stress and the general effects on the body:
Prepares the body for action: increases heart rate, dilates airways and pupils, decreases digestion and urinary activity, mobilizes energy stores.
Describe the role of the parasympathetic division during rest and the general effects on the body:
Promotes energy conservation and routine maintenance: slows heart rate, enhances digestion, stimulates salivation, urination, and defecation.
Differentiate between cholinergic and adrenergic neurons:
Cholinergic neurons release acetylcholine (ACh); found in all preganglionic neurons and parasympathetic postganglionic neurons.
Adrenergic neurons release norepinephrine (NE); found in most sympathetic postganglionic neurons.
Contrast the two types of cholinergic receptors:
Nicotinic receptors: Found on postganglionic neurons; always excitatory.
Muscarinic receptors: Found on effector cells; can be excitatory or inhibitory depending on the organ.
Describe the types of adrenergic receptors and their subtypes:
Alpha receptors:
Alpha-1: Generally excitatory (e.g., vasoconstriction)
Alpha-2: Often inhibitory (presynaptic inhibition)
Beta receptors:
Beta-1: Increases heart rate and contraction
Beta-2: Causes bronchodilation and vasodilation
Beta-3: Involved in lipolysis in adipose tissue
Alpha receptors:
Alpha-1: Generally excitatory (e.g., vasoconstriction)
Alpha-2: Often inhibitory (presynaptic inhibition)
